Preflop: I think flatting here is fine. If BU raised instead of CO, I think A3s becomes much stronger and I would call with that. But here either line is fine.

Flop: 90c should suffice - No need to bet more than required. IF he has nothing he's folding anyway. And the additional 20c invested wouldn't justify the additional fold equity generated.

Turn: This is not a good barrel card. It doesn't strengthen your perceived range in anyway and it widens your perceived range actually by adding more draws. if he has midpairs here, he's more inclined to call twice with those. And I don't like the idea of blindly firing thrice with no equity.